What does "Ex" stand for in Windows API function names?
I was under the impression it stood for extended, as in a more detailed interface for that particular library.
For example, CreateFile with 4 parameters is the typical version and CreateFileEx with 17 is the version offering more control and finer detail over how the file is opened, what occurs if it doesn't exist, etc, and is thus extended.
When Microsoft updates a function and the new function is incompatible with the old one, Microsoft continues to support the old function. The new function keeps the same name as the old function, with added -Ex suffix.